Ultraviolet curable resin composition and photo solder resist ink including the same

ABSTRACT

An ultraviolet curable resin composition comprises (A) an ultraviolet curable resin obtained by reacting an epoxy group containing polymer (a), which is prepared by polymerizing an ethylenically unsaturated monomer component including an ethylenically unsaturated monomer (i) having an epoxy group, with an ethylenically unsaturated monomer (b) having a carboxyl group, and then reacting a resultant intermediate product with a saturated or unsaturated polybasic acid anhydride (c); (B) an epoxy compound having at least two epoxy groups in molecule; (C) a photopolymerization initiator; and (D) a diluent The ultraviolet curable resin includes 0.3 to 10 mol of a polymerizable unsaturated group in 1 kg thereof. A photo solder resist ink containing this resin composition has the capability of providing a permanent film with excellent flexibility and solder heat resistance, and is preferably used to manufacture flexible printed circuit boards.

TECHNICAL FIELD

[0001] The present invention relates to an ultraviolet curable resincomposition having the capability of forming a cured film with excellentflexibility and solder heat resistance, and a photo solder resist inkincluding the same resin composition.

BACKGROUND ART

[0002] In recent years, demand for flexible printed circuit boards usinga film-like substrate such as a polyester film or a polyimide film isgrowing. However, there is a problem that a permanent film formed by useof a conventional photo solder resist ink developable with a dilutedalkali aqueous solution is poor in flexibility despite good solder heatresistance. Due to this reason, it has been difficult to use the resistink to the flexible printed circuit board (FPC) requiring theflexibility.

[0003] For example, photo solder resist inks available to manufacturethe flexible printed circuit boards were proposed in Japanese PatentEarly Publication [kokai] Nos. 7-207211, 8-274445 and 9-5997. However,sufficient flexibility has not been achieved yet. In addition, there isa case of lowering the solder heat resistance when trying to improve theflexibility. Thus, the photo solder resist ink having sufficientperformance has not been obtained under the present circumstances.

SUMMARY OF THE INVENTION

[0004] In view of the above problems, a concern of the present inventionis to provide an ultraviolet curable resin composition having thecapability of forming a cured film with good flexibility as well asimproved solder heat resistance. That is, the ultraviolet curable resincomposition of the present invention comprises:

[0005] (A) an ultraviolet curable resin obtained by reacting an epoxygroup containing polymer (a), which is prepared by polymerizing anethylenically unsaturated monomer component including an ethylenicallyunsaturated monomer (i) having an epoxy group and a compound (ii) havingat least two ethylenically unsaturated groups in one molecule, with anethylenically unsaturated monomer (b) having a carboxyl group, and thenreacting a resultant intermediate product with a saturated orunsaturated polybasic acid anhydride (c), the ultraviolet curable resinincluding 0.3 to 10 mol of a polymerizable unsaturated group in 1 kgthereof;

[0006] (B) an epoxy compound having at least two epoxy groups inmolecule;

[0007] (C) a photopolymerization initiator; and

[0008] (D) a diluent.

[0009] A further concern of the present invention is to provide a photosolder resist ink including the above resin composition. This photosolder resist ink is optimum to manufacture flexible printed circuitboards, and can provide a permanent film having excellent flexibilityand solder heat resistance.

[0010] Another concern of the present invention is to provide a flexibleprinted circuit board or a printed circuit board, which has a permanentfilm formed by use of the above-described photo solder resist ink.

[0011] Still another concern of the present invention is to provide adry film obtained by forming a film of the ultraviolet curable resincomposition or the photo solder resist ink described above on a support.This dry film can provide a permanent film having excellent flexibilityand solder heat resistance to the printed circuit board or the flexibleprinted circuit board.

[0012] These and still other objects and advantages of the presentinvention will become apparent from the best mode for carrying out theinvention explained below referring to the attached drawings.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013] An ultraviolet curable resin (A) used in the present invention isan ultraviolet curable resin obtained by reacting an epoxy groupcontaining polymer (a), which is prepared by polymerizing anethylenically unsaturated monomer component including an ethylenicallyunsaturated monomer (i) having an epoxy group, with an ethylenicallyunsaturated monomer (b) having a carboxyl group, and then reacting aresultant intermediate product with a saturated or unsaturated polybasicacid anhydride (c). The ultraviolet curable resin includes 0.3 to 10 molof a polymerizable unsaturated group in 1 kg thereof.

[0014] As the epoxy group containing polymer (a), it is possible to usea copolymer obtained by polymerizing the ethylenically unsaturatedmonomer component, which includes the ethylenically unsaturated monomer(i) having the epoxy group and an ethylenically unsaturated monomer(iii) copolymerizable with this monomer (i).

[0015] In addition, as the epoxy group containing polymer (a), it ispossible to use a copolymer obtained by polymerizing the ethylenicallyunsaturated monomer component, which includes the ethylenicallyunsaturated monomer (i) having the epoxy group and a compound (ii)having at least two ethylenically unsaturated groups in one molecule.

[0016] Moreover, as the epoxy group containing polymer (a), it ispossible to use a copolymer obtained by polymerizing the ethylenicallyunsaturated monomer component, which includes the ethylenicallyunsaturated monomer (i) having the epoxy group, a compound (ii) havingat least two ethylenically unsaturated groups in one molecule, and anethylenically unsaturated monomer (iii) copolymerizable with them.

[0017] When using the ethylenically unsaturated monomer component notincluding the compound (ii) and the ethylenically unsaturated monomer(iii), it is preferred that a content of the ethylenically unsaturatedmonomer (i) is 100 mol % with respect to a total amount of theethylenically unsaturated monomer component used to prepare the epoxygroup containing polymer (a).

[0018] The ethylenically unsaturated monomer (i) brings the epoxy groupin the epoxy group containing polymer (a). By the addition of theethylenically unsaturated monomer having the carboxyl group,photocurability resulting from an ethylenically unsaturated double bondis given to the epoxy group containing polymer (a).

[0019] As the ethylenically unsaturated monomer (i), for example, it ispossible to use glycidyl (meth)acrylate, an epoxy cyclohexyl derivativeof (meth)acrylic acid such as (3, 4-epoxy cyclohexyl)methyl(meth)acrylate, an alicyclic epoxy derivative of (meth)acrylate,β-methylglycidyl (meth)acrylate and monoallyl diglycidyl isocyanurate.One of these compounds or a combination thereof can be used as theethylenically unsaturated monomer (i). In particular, it is preferred touse glycidyl (meth)acrylate that is easy to get. In the presentspecification, “(meth)acrylic acid” is a generic name for “acrylic acid”and “methacrylic acid”, and “(meth)acrylic-” is a generic name for“acrylic-” and “methacrylic-”.

[0020] The compound (ii) is an optional component used for the purposeof further improving heat resistance and softening point of theultraviolet curable resin composition of the present invention. In thecase of using the compound (ii), it is preferred that a content of thecompound (ii) is within a range of 0.1 to 10 mol % with respect to atotal amount of the ethylenically unsaturated monomer component used toprepare the epoxy group containing polymer (a). In this range, thepolymerization for generating the epoxy group containing polymer (a) canproceed under a preferred condition. In particular, it is effective toprevent gelation. In addition, a cured film formed by the ultravioletcurable resin composition of the present invention exhibits excellentheat resistance. When using the cured film as a solder resist, excellentsolder heat resistance can be obtained. When the content is within arange of 0.1 to 7 mol %, there is an advantage that both of improvedheat resistance and good polymerization can be simultaneously achieved.

[0021] As the compound (ii) having at least two ethylenicallyunsaturated groups in one molecule, for example, it is possible to use acompound having two ethylenically unsaturated groups in one moleculesuch as diethylene glycol di(meth)acrylate, triethylene glycoldi(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropyleneglycol di(meth)acrylate, EOPO-denatured di(meth)acrylate, bisphenol AEOadduct di(meth)acrylate, bisphenol FEO adduct di(meth)acrylate,bisphenol APO adduct di(meth)acrylate, bisphenol AEOPO adductdi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, trimethylol propane di(meth)acrylate, cyclopentanyldi(meth)acrylate, or cyclopentenyl di(meth)acrylate, and diallylmonoglycidyl isocyanurate.

[0022] In addition, it is possible to use a compound having three ormore of ethylenically unsaturated groups in one molecule such astrimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, dipentaerythritolpenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, di-, tri- ormore polyester obtained by a reaction between a polybasic acid andhydroxyalkyl (meth)acrylate, and polyester (meth)acrylate. One of thesecompounds or a combination thereof can be used as the compound (ii).

[0023] When the epoxy group containing polymer (a) contains theabove-described compound (ii), its principal chain is reinforced, sothat effects of improving the solder heat resistance, developing widthand regulating the softening point can be achieved. The developing widthmeans a width of predrying condition, in which developability can bemaintained, and is also called a predrying control width or predryingacceptable range.

[0024] Specifically, it is preferred to use di(meth)acrylate as thecompound (ii). As di(meth)acrylate, for example, it is particularlypreferred to use a compound having at least one oxyalkylene unit inmolecule such as oxyethylene or oxypropylene. In this case, it ispossible to improve the solder heat resistance of the ultravioletcurable resin composition of the present invention, and particularlyprovide excellent developing width. It is preferred that the number ofoxyalkylene unit in one molecule of di(meth)acrylate is within a rangeof 1 to 40, preferably 4 to 30, and more preferably 4 to 10. When thiscondition is satisfied, the reaction of preparing the ultravioletcurable resin (A) stably proceeds, so that the developing width of theultraviolet curable resin composition increases, and the solder heatresistance of a cured film thereof is improved.

[0025] In addition, when using di(meth)acrylate having the oxyalkyleneunit and a bisphenol skeleton, it is possible to provide remarkablyimproved solder heat resistance and developing width.

[0026] As di(meth)acrylate having the oxyalkylene unit available as thecompound (ii), it is possible to use polyethylene glycol dimethacrylateor ethylene glycol dimethacrylate, which is represented by the followinggeneral formula (1):

[0027] wherein a value of “n” in the formula is an integer selected froma range of 1 to 40.

[0028] Alternatively, it is possible to use polypropylene glycoldimethacrylate or propylene glycol dimethacrylate, which is representedby the following general formula (2):

[0029] wherein values of “n” and “m” in the formula are respectively aninteger of 0 or more determined such that a sum of “n” and “m” is withina range of 1 to 40.

[0030] In addition, it is possible to use polyethylene glycol diacrylateor ethylene glycol diacrylate, which is represented by the followinggeneral formula (3):

CH₂═CH—CO—O(CH₂—CH₂O)_(n)OC—CH═CH₂  (3)

[0031] wherein a value of “n” in the formula is an integer selected froma range of 1 to 40.

[0032] In addition, as the di(meth)acrylate having the oxyalkylene unitand the bisphenol skeleton, it is possible to use a compound representedby the following general formula (4).

[0033] wherein values of “n” and “m” in the formula are respectively aninteger of 0 or more determined such that a sum of “n” and “m” is withina range of 1 to 40. As such a compound, for example, it is possible touse 2,2-bis[4-(methacryloxy ethoxy)phenyl] propane,2,2,-bis[4-(methacryloxy.diethoxy)phenyl] propane,2,2-bis[4-(methacryloxy.polyethoxy)phenyl] propane, or the like.

[0034] Alternatively, it is possible to use a compound represented bythe following general formula (5):

[0035] wherein values of “n” and “m” in the formula are respectively aninteger of 0 or more determined such that a sum of “n” and “m” is withina range of 1 to 40. For example, as such a compound, it is possible touse 2,2-bis[4-(acryloxy ethoxy)phenyl] propane,2,2-bis[4-(acryloxy.diethoxy)phenyl] propane,2,2-bis[4-(acryloxy.polyethoxy)phenyl] propane, bisphenol-A polyethyleneglycol polypropylene glycol adduct dimethacrylate, or the like.

[0036] Specifically, as the di(meth)acrylate having oxyalkylene unit,for example, it is possible to use “NK Ester 4G” represented by theformula (1) [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polyethylene glycol #200 dimethacrylate (average value of “n”: 4)], “NKEster 9G” represented by the formula (1) [manufactured by SHINNAKAMURACHEMICAL INDUSTRIAL CO., LTD., polyethylene glycol #400 dimethacrylate(average value of “n”: 9)], “NK Ester 9PG” represented by the formula(2) [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polypropylene glycol #400 dimethacrylate (average value of “m+n”: 7)],“NK Ester A-200” represented by the formula (3) [manufactured bySHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD., polyethylene glycol #200diacrylate (average value of “n”: 4)], “NK Ester A-400” represented bythe formula (3) [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO.,LTD., polyethylene glycol #400 diacrylate (average value of “n”: 9)],and “NK Ester A-600” expressed by the formula (3) [manufactured bySHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD., polyethylene glycol #600diacrylate (average value of “n”: 14)].

[0037] On the other hand, as the di(meth)acrylate having oxyalkyleneunit and bisphenol skeleton, for example, it is possible to use “NKEster-BPE-100” represented by the formula (4) [manufactured bySHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD., 2,2-bis[4-(methacryloxyethoxy)phenyl] propane (average value of “n+m”: 2.6)], “NKEster-BPE-200” represented by the formula (4) [manufactured bySHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,2,2-bis[4-(methacryloxy.diethoxy)phenyl] propane (average value of“n+m”: 4)], “NK Ester-BPE-500” represented by the formula (4)[manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,2,2-bis[4-(methacryloxy.polyethoxy)phenyl] propane (average value of“n+m”: 10)], “NK Ester A-BPE-4” represented by the formula (5)[manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,2,2-bis[4-(acryloxy.diethoxy)phenyl] propane (average value of “n+m”:4)], and “Blemmer 43 DB-40B” [manufactured by NOF Corp., bisphenol-Apolyethylene glycol polypropylene glycol adduct dimethacrylate].

[0038] The ethylenically unsaturated monomer (iii) copolymerizable withthe ethylenically unsaturated monomer (i) having the epoxy group and thecompound (ii) having at least two ethylenically unsaturated groups inone molecule is an optional component, which is used to control thephotocurability of the ultraviolet curable resin composition of thepresent invention and solid state properties of a cured film thereof, ifnecessary.

[0039] The ethylenically unsaturated monomer (iii) is not specificallylimited. For example, it is possible to use a straight-chained orbranch-chained alkyl ester of (meth)acrylic acid, (meth)acrylic acidalicyclic ester (an unsaturated bond may be included in the ring.) suchas methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate,2-ethyl hexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl(meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, myristyl(meth)acrylate, cetyl (meth)acrylate, stearyle (meth)acrylate,cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate, ethylene glycolester (meth)acrylate such as hydroxy ethyl (meth)acrylate, methoxy ethyl(meth)acrylate, ethoxy ethyl (meth)acrylate, diethylene glycolmono(meth)acrylate, triethylene glycol mono(meth)acrylate and methoxydiethylene glycol mono(meth)acrylate, propylene glycol (meth)acrylate,butylene glycol mono(meth)acrylate, glycerol mono(meth)acrylate, oraromatic (meth)acrylate such as benzyl (meth)acrylate, a(meth)acrylamide compound such as (meth)acrylamide, N-methyl(meth)acrylamide, N-propyl (meth)acrylamide, N-t-butyl (meth)acrylamide,N-t-octyl (meth)acrylamide and diacetone (meth)acrylamide, a maleimidecompound such as N-phenyl maleimide, N-(2-methyl phenyl) maleimide,N-cyclohexyl maleimide, N-(2,6-diethyl phenyl) maleimide, N-laurylmaleimide and N-benzyl maleimide, vinyl pyrrolidone,(meth)acrylonitrile, vinyl acetate, styrene, α-methyl styrene, or vinylether. One of these compounds or a combination thereof can be used asthe ethylenically unsaturated monomer (iii).

[0040] In particular, it is preferred to use the straight-chained orbranch-chained alkyl ester of (meth)acrylic acid, (meth)acrylic acidfatty ester, (meth)acrylic acid aromatic ester, (meth)acrylic acidalicyclic ester (an unsaturated bond may be included in the ring.),hydroxyalkyl (meth)acrylate, alkoxyalkyl (meth)acrylate, or themaleimide compound because it becomes easy to control the hardness of afilm of the ultraviolet curable resin composition, the oiliness thereof,and the hardness of a finally-formed resist.

[0041] When using the ethylenically unsaturated monomer (iii), it ispreferred that a content thereof is within a range of 1 to 60 mol %,preferably 1 to 55 mol %, and more preferably 10 to 50 mol % withrespect to the total amount of the ethylenically unsaturated monomercomponent. In this range, it is possible to bring a sufficient amount ofethylenically unsaturated groups into the ultraviolet curable resin (A).In addition, it becomes easy to control the hardness and hydrophilicityof the cured film.

[0042] The epoxy group containing polymer (a) can be prepared accordingto a conventional polymerization method such as solution polymerizationor emulsion polymerization. For example, when adopting the solutionpolymerization, a polymerization initiator is added to the ethylenicallyunsaturated monomer component including the ethylenically unsaturatedmonomer (i) and if necessary the ethylenically unsaturated monomer (iii)and the compound (ii) in the presence of a suitable organic solvent.Then, a resultant mixture is heated in a nitrogen gas flow, while beingagitated. Alternatively, a polymerization method may be performed undera reflux.

[0043] As the organic solvent used in the above polymerization, forexample, it is possible to use ketone such as methyl ethyl ketone andcyclohexanone, aromatic hydrocarbon such as toluene and xylene, aceticester such as ethyl acetate, butyl acetate, cellosolve acetate, butylcellosolve acetate, butyl carbitol acetate and propylene glycolmonomethyl ether acetate, or dialkyl glycol ether. One of thesecompounds or a mixture thereof can be used as the organic solvent.

[0044] As the polymerization initiator for polymerization, for example,it is possible to use a peroxide such as t-butyl hydroperoxide,di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide and di-isopropylperoxy dicarbonate, or an azo compound such as azobisisobutylonitrile,2,2′-azobisisomethyl butyrate and azobiscyanovaleronitrile. One of thesecompounds or a combination thereof can be used as the polymerizationinitiator.

[0045] The ultraviolet curable resin (A) can be obtained by reacting theepoxy group containing polymer (a) with the ethylenically unsaturatedmonomer (b) having the carboxyl group, and then carrying out a reactionof adding the saturated or unsaturated polybasic acid anhydride (c) tothe resultant intermediate product.

[0046] As the ethylenically unsaturated monomer (b) having carboxylgroup, for example, it is possible to use (meth)acrylic acid, crotonicacid, cinnamic acid, a compound having a single ethylenicallyunsaturated group such as 2-(meth)acryloyloxyethyl succinic acid,2-(meth)acryloyloxyethyl phthalic acid, β-carboxyethyl acrylate,acryloyloxyethyl succinate, 2-propenoic acid,3-(2-carboxyethoxy)-3-oxopropyl ester, 2-(meth)acryloyloxyethyltetrahydrophthalic acid, and 2-(meth)acryloyloxyethyl hexahydrophthalicacid, or a compound having a plurality of ethylenically unsaturatedgroups, e.g., a compound obtained by reacting a dibasic acid anhydridewith a polyfunctional acrylate having hydroxyl group such asdipentaerythritol penta(meth)acrylate, trimethylol-propanedi(meth)acrylate, pentaerythritol tri(meth)acrylate. One of thesecompounds or a combination thereof as the ethylenically unsaturatedmonomer (b). It is preferred to use the compound having the singlecarboxyl group, and particularly (meth)acrylic acid, or a compoundcontaining (meth)acrylic acid as the main ingredient. A reason for using(meth)acrylic acid as the ethylenically unsaturated monomer (b) is inthat the ethylenically unsaturated group supplied from (meth)acrylicacid is excellent in photoreactivity.

[0047] It is preferred that a compounding amount of the ethylenicallyunsaturated monomer (b) is determined such that an amount of carboxylgroup of ethylenically unsaturated monomer (b) per 1 mol of epoxy groupof the epoxy group containing polymer (a) used to prepare theultraviolet curable resin (A) is within a range of 0.7 to 1.2 mol,preferably 0.9 to 1.1 mol, and more preferably 0.95 to 1.1 mol. In theabove range, the ultraviolet curable resin composition of the presentinvention can provide a remarkably wide developing width. In addition,it is possible to minimize an influence of the remaining ethylenicallyunsaturated monomer (b) having unreacted carboxyl group.

[0048] As the saturated or unsaturated polybasic acid anhydride (c), forexample, it is possible to use a dibasic acid anhydride such as succinicanhydride, methyl succinic anhydride, maleic anhydride, citraconicanhydride, glutaric anhydride, itaconic anhydride, phthalic anhydride,tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride,methyl nadic acid anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride, or a polybasic acid anhydride such astrimellitic acid anhydride, pyromellitic acid anhydride, benzophenonetetracarboxylic anhydride and methyl cyclohexene tetracarboxylicanhydride. One of these compounds or a combination thereof can be usedas the polybasic acid anhydride (c).

[0049] The principal purpose of compounding the saturated or unsaturatedpolybasic acid anhydride (c) is to provide an acid value to theultraviolet curable resin (A) such that the ultraviolet curable resinhas re-dispersion and re-dissolution properties with a diluted alkalineaqueous solution as well as thermosetting property. It is preferred thata compounding amount of the polybasic acid anhydride (c) is determinedsuch that the acid value of the ultraviolet curable resin obtained bythe addition of the polybasic acid anhydride (c) is within a range of 25to 150 mgKOH/g, and particularly 45 to 100 mgKOH/g. In this range, theultraviolet curable resin composition of the present invention exhibitsgood developing property, and a cured film formed thereby is excellentin electric properties, electrical corrosion resistance, and waterresistance. When the acid value is within the range of 50 to 85 mgKOH/g,particularly preferred results are obtained.

[0050] The addition reactions of the ethylenically unsaturated monomer(b) having the carboxyl group to the copolymer and the saturated orunsaturated polybasic acid anhydride (c) can be performed by aconventional method. For example, the addition reaction of theethylenically unsaturated monomer (b) can be performed by adding theethylenically unsaturated monomer (b), methoxy hydroquinone as a thermalpolymerization inhibitor and a catalyst such as a tertiary amine,quaternary ammonium salt or triphenyl stibine to the epoxy groupcontaining polymer (a), mixing and agitating a resultant mixture, andreacting the mixture at a reaction temperature of 60 to 150° C., andpreferably 80 to 120° C. according to the conventional method. Theaddition reaction of the saturated or unsaturated polybasic acidanhydride (c) can be performed according to a substantially same methodas the above.

[0051] It is required that the obtained ultraviolet curable resin (A)includes 0.3 to 10 mol, and more preferably 0.5 to 8 mol of apolymerizable unsaturated group in 1 kg thereof. In this case, it ispossible to provide a permanent film having excellent flexibility andflexural endurance by use of a photo solder resist ink containing theultraviolet curable resin composition of the present invention. Thus,the photo solder resist ink of the present invention is particularlysuitable to manufacture a flexible printed circuit board using afilm-like substrate such as polyester or polyimide.

[0052] A weight-average molecular weight of the ultraviolet curableresin (A) is not specifically limited. However, it is preferred that theweight-average molecular weight is within a range of 3000 to 400000. Inthis range, the ultraviolet curable resin composition exhibits excellentsensitivity and resolution.

[0053] To stably provide good sensitivity and workability of theultraviolet curable resin composition of the present invention and goodproperties of a resist film thereof, it is preferred that a compoundingamount of the ultraviolet curable resin (A) is within a range of 10 to80 wt % with respect to a total amount of the components of theultraviolet curable resin composition of the present invention exceptfor the organic solvent in the diluent (D). In this range, it ispossible to remarkably improve the ultraviolet curability of theultraviolet curable resin composition and reduce the surface tackinessof a predried film thereof.

[0054] As the epoxy compound (B) having at least two epoxy groups in onemolecule, for example, an epoxy compound that is hardly soluble insolvent or an epoxy compound that is soluble in solvent can be used.Specifically, it is possible to use phenol novolac-type epoxy resin,cresol novolac-type epoxy resin, bisphenol A-type epoxy resin, bisphenolA-novolac-type epoxy resin, bisphenol F-type epoxy resin, triglycidylisocyanurate, monoallyl diglycidyl isocyanurate, YX 4000 (manufacturedby Yuka Shell Epoxy Kabushiki Kaisha), sorbitol polyglycidyl ether,N-glycidyl-type epoxy resin, alicyclic-type epoxy resin (e.g.,“EHPE-3150” manufactured by Daicel Chemical Industries, Ltd.), polyolpolyglycidyl ether compound, glycidyl ester compound, N-glycidyl epoxyresin, tris (hydroxyphenyl)methane-based polyfunctional epoxy resin(e.g., “EPPN-502H” manufactured by NIPPON KAYAKU Co., LTD. or“TACTIX-742” and “XD-9053” manufactured by DOW CHEMICAL), hydrogenatedbisphenol A-type epoxy resin, dicyclopentadiene-phenol-type epoxy resin,naphthalene-type epoxy resin, or a vinyl polymerization polymer havingepoxy group. One of these compounds or a combination thereof can be usedas the epoxy compound (B). In addition, these compounds may have amodification by crosslinking. In particular, it is preferred to usetriglycidyl isocyanurate, YX 4000, phenol novolac-type epoxy resin,cresol novolac-type epoxy resin, bisphenol A-type epoxy resin, orbisphenol A-novolac-type epoxy resin.

[0055] It is preferred that a compounding amount of the epoxy compound(B) is within a range of 0.1 to 50 wt % with respect to the total amountof the components of the ultraviolet curable resin composition of thepresent invention except for the organic solvent in the diluent (D). Inthis range, the ultraviolet curable resin composition exhibits excellentthermosetting property, and a remarkably wide developing width.

[0056] As the photopolymerization initiator (C), for example, it ispossible to use benzoin, an alkyl ether of benzoin such as benzoinmethyl ether, benzoin ethyl ether and benzoin isopropyl ether,acetophenone such as acetophenone, 2,2-dimethoxy-2-phenyl acetophenone,2,2-diethoxy-2-phenyl acetophenone, 1,1-dichloroacetophenone and1-hydroxy cyclohexyl phenylketone, anthraquinone such as 2-methylanthraquinone and 2-amyl anthraquinone, thioxanthone such as2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone,2-chlorothioxanthone, 2,4-diisopropyl thioxanthone and1-chloro-4-propoxy thioxanthone, ketal such as acetophenonedimethylketal and benzyl dimethyl ketal, benzophenone or xanthone suchas 3,3-dimethyl-4-methoxy benzophenone, 3,3′, 4,4′-tetra-(t-butylperoxyl carbonyl) benzophenone and 4-benzoyl-4′-methyl diphenyl sulfido,nitrogen containing compound such as2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-on,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1 and4,4′-bis-diethyl aminobenzophenone, or 2,4,6-trimethyl benzoyidiphenylphosphine oxide. These compounds may be used together with aconventional photopolymerization enhancer or sensitizer such as benzoicacid, and tertiary amine, e.g., p-dimethyl aminobenzoic acid ethylester, p-dimethyl aminobenzoic acid isoamyl ester, and 2-dimethylaminoethyl benzoate. One of these compounds or a combination of thereofcan be used as the photopolymerization initiator (C).

[0057] In addition, as a sensitizer for laser exposure, for example, itis possible to use a coumarin derivative such as7-dimethylamino-4-methylcoumarin, 4,6-diethyl-7-ethylaminocoumarin, or ametallocene such as carbocyanine dye, xanthene dye,bis(η⁵-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium. In this case, it is possible to allow the ultraviolet curableresin composition to exhibit near-infrared curability or visual-lightcurability.

[0058] To achieve good balance between photocurability and properties ofthe solder resist, it is preferred that a compounding amount of thephotopolymerization initiator (C) is within a range of 0.1 to 30 wt %with respect to the total amount of the components of the ultravioletcurable resin composition of the present invention except for theorganic solvent in the diluent (D). In this range, the ultravioletcurable resin composition exhibits excellent ultraviolet curability aswell as remarkably improved heat resistance and electrical corrosionresistance of a cured film thereof.

[0059] As the diluent (D), one of an ethylenically unsaturatedphotopolymerizable monomer (D-1), an organic solvent (D-2) or a mixturethereof can be used. As the ethylenically unsaturated monomer (D-1), forexample, it is possible to use 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, N-vinyl pyrrolidone, (meth)acryloylmorpholine, methoxy tetraethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycoldi(meth)acrylate, N,N-dimethyl (meth)acrylamide, N-methylol(meth)acrylamide, N,N-dimethyl aminopropyl (meth)acrylamide,N,N-dimethyl aminoethyl (meth)acrylate, N,N-dimethyl aminopropyl(meth)acrylate, melamine (meth)acrylate, diethylene glycoldi(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, tripropylene glycol di(meth)acrylate, phenoxyethyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, cyclohexyl(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,dipentaerythritol hexa(meth)acrylate, isobonyl (meth)acrylate,cyclopentanyl mono(meth)acrylate, cyclopentenyl mono(meth)acrylate,trimethylolpropane EO-denatured triacrylate, cyclopentanyldi(meth)acrylate, cyclopentenyl di(meth)acrylate, mono-, di-, tri- ormore polyester of polybasic acid and hydroxyalkyl (meth)acrylate, or a(meth)acrylate monomer such as polyester (meth)acrylate and urethane(meth)acrylate. One of these compounds or a combination thereof can beused.

[0060] As the organic solvent (D-2), for example, it is possible to usea straight-chained, branch-chained, secondary or multiple alcohol suchas ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutylalcohol, 2-butyl alcohol, hexanol, and ethylene glycol, ketone such asmethyl ethyl ketone and cyclohexanone, aromatic hydrocarbon such astoluene and xylene, an oil aromatic mixture solvent such as “SWASOLSERIES” (manufactured by Maruzen Petrochemical Co., Ltd.), “SOLVESSOSERIES” (manufactured by EXXON CHEMICAL COMPANY), cellosolve such ascellosolve and butyl cellosolve, carbitol such as carbitol and butylcarbitol, propylene glycol alkyl ether such as propylene glycol methylether, polypropylene glycol alkyl ether such as dipropylene glycolmethyl ether, acetic ester such as ethyl acetate, butyl acetate,cellosolve acetate, butyl cellosolve acetate, butyl carbitol acetate andpropylene glycol monomethyl ether acetate, or dialkyl glycol ether. Oneof these compounds or a combination of thereof can be used as theorganic solvent.

[0061] The ethylenically unsaturated photopolymerizable monomer (D-1)used as the diluent (D) dilutes the ultraviolet curable resin (A) toprovide easiness of applying the resin composition and adjusts the acidvalue of the resin composition to obtain suitable photocurability. Inaddition, the organic solvent (D-2) used as the diluent (D) dissolvesand dilutes the ultraviolet curable resin composition (A), so that theliquid resin composition can be easily applied, and then dried to obtaina film.

[0062] When the diluent (D) contains the ethylenically unsaturatedphotopolymerizable monomer (D-1), it is preferred that the component(D-1) includes 3 to 12 mol of a polymerizable unsaturated group in 1 kgthereof. In this range, the photo solder resist ink including theultraviolet curable resin composition of the present invention canprovide a permanent film having remarkably improved flexibility andflexural endurance. As a result, the photo solder resist ink of thepresent invention becomes suitable to manufacture a flexible printedcircuit board using a film-like substrate such as polyester orpolyimide.

[0063] By the way, the ultraviolet curable resin composition of thepresent invention does not necessarily require the ethylenicallyunsaturated photopolymerizable monomer (D-1) as the diluent (D).However, when using the ethylenically unsaturated photopolymerizablemonomer (D-1) in the diluent (D), it is preferred that the compoundingamount is 50 wt % or less with respect to the total amount of componentsof the ultraviolet curable resin composition of the present inventionexcept for the organic solvent in the diluent (D). When the compoundingamount is more than 50 wt %, there is a fear of increasing the surfacetackiness of the predried film. Therefore, when a negative photomaskhaving a required pattern is directly put on the predried film, and thenexposure is performed, a contamination of the photomask may happen.

[0064] On the other hand, the organic solvent (D-2) used as the diluent(D) is an essential component to obtain the ultraviolet curable resincomposition developable with a diluted alkali aqueous solution. It isrequired that the organic solvent can be rapidly evaporated from theresin composition by predrying without being left in the predried film.It is preferred that a compounding amount of the organic solvent is 5 wt% or more with respect to the total amount of components of theultraviolet curable resin composition of the present invention. When thecompounding amount is less than 5 wt %, there is a fear that it becomesdifficult to uniformly apply the resin composition. An upper limit ofthe compounding amount of the organic solvent is not specificallylimited because a suitable compounding amount of the organic solvent isdetermined according to an applying method used.

[0065] Besides the above-explained components, the ultraviolet curableresin composition of the present invention may contain a blockedisocyanate, a thermosetting component such as amino resin, ultravioletcurable epoxy (meth)acrylate, for example, a first compound obtained byadding (meth)acrylic acid to a bisphenol A-type, phenol novolac-type,cresol novolac-type or an alicyclic epoxy resin, a second compoundobtained by adding a saturated or unsaturated polybasic acid anhydridesuch maleic anhydride, succinic anhydride, itaconic anhydride, phthalicanhydride and tetrahydrophthalic anhydride to the first compound, anultraviolet curable polymer obtained by reacting hydroxyalkyl(meth)acrylate, (meth)acrylate having epoxy group with a copolymer ofmaleic anhydride and the other ethylenically unsaturated monomer, acopolymer of an ethylenically unsaturated compound such asstyrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, anultraviolet curable polymer obtained by reacting an ethylenicallyunsaturated monomer having epoxy group with the copolymer, anultraviolet curable polymer obtained by adding (meth)acrylic acid to avinyl copolymer containing the ethylenically unsaturated monomer havingepoxy group as a monomer unit, or a high molecular compound such asstyrene-maleic resin, diallyl phthalate resin, phenoxy resin, melamineresin, urethane resin, and a fluorine containing resin.

[0066] If necessary, the ultraviolet curable resin composition of thepresent invention may contain an additive such as an epoxy resin curingagent, curing enhancer, filler, coloring agent, leveling agent, adhesionsupplying agent, thixotropic agent, polymerization inhibitor,antihalation agent, flame retardant, defoamer, dispersion stabilizingagent, high molecular dispersing agent and an anti-oxidant.

[0067] The ultraviolet curable resin composition of the presentinvention can be obtained by kneading the above-explained components andthe additives with a conventional kneading means such as three rolls,ball mill and sand mill. For example, a first mixture is prepared bymixing a part of components (A) to (D), for example, a part of thecomponent (D) with the component (B), and on the other hand, a secondmixture is prepared by mixing the components (A) and (C) with the restof the component (D). In this case, the first mixture may be mixed withthe second mixture according to the compounding amounts described aboveat the time of using the resin composition of the present invention.

[0068] Directions for use of the ultraviolet curable resin compositionof the present invention are not specifically limited. For example, theultraviolet curable resin composition can be used as the photo solderresist ink that is preferable to manufacture a printed circuit boardhaving a high-density, fine conductive pattern. By use of this photosolder resist ink, a resist pattern can be formed on the printed circuitboard or a substrate. In this case, by curing the pattern of the photosolder resist ink formed on the printed circuit board or the substrate,a resist pattern of a cured film thereof can be obtained.

[0069] As an example, the resist pattern can be formed on the substrateaccording to the following method. First, the photo solder resist ink isapplied on the substrate by use of dipping, spraying, spin coating, rollcoating, curtain coating, screen printing, and so on. Then, tovolatilize the organic solvent of the diluent from the applied film,predrying is performed at a temperature of 60 to 120° C., to therebyobtain a predried film.

[0070] Next, a negative mask having a required pattern is directly orindirectly put on the predried film, and ultraviolet is radiated to thepredried film through the mask by use of a chemical lamp, low-pressuremercury lamp, intermediate-pressure mercury lamp, high-pressure mercurylamp, ultra-high-pressure mercury lamp, xenon lamp, metalhalide lamp,and so on. Then, developing is performed to obtain a pattern. Inaddition, a heat treatment is performed at a temperature of 120 to 180°C. for 30 to 90 minutes to cure the epoxy compound, to obtain a resistpattern of a cured film having excellent film strength, hardness andchemical resistance.

[0071] This cured film can be used as a permanent mask. That is, byusing a printed circuit board as a substrate, which is obtained byforming a conductive pattern on an insulating layer of an insultingmaterial such as resins or ceramics by a conventional printingtechnique, and forming a permanent film on this substrate, it ispossible to provide the printed circuit board with the permanent filmhaving excellent flexibility and solder heat resistance.

[0072] In addition, since the photo solder resist ink including theultraviolet curable resin composition of the present invention has anadvantage that the cured film exhibits excellent flexibility and solderheat resistance, it is suitable to form the permanent film for aflexible printed circuit board. In this case, the permanent film can beformed on a wiring board, which is obtained by forming a conductivepattern on a substrate of a plastic film having flexibility andelectrical insulation such as polyester or polyimide according to theconventional printing technique.

[0073] In addition, it is possible to provide a dry film resist byforming a film of the ultraviolet curable resin composition or the photosolder resist ink of the present invention on a support. In this case,it is preferred that the film thickness is within a range of 10 to 100μm, and a film having a thickness of 5 to 100 μm such as polyethyleneterephthalate is used the support. The dry film of the ultravioletcurable resin composition or the photo solder resist ink can be obtainedby applying it on the film that is the support, and drying the appliedfilm.

[0074] As an alkaline solution used in the developing step, for example,it is possible to use an aqueous solution of sodium carbonate, potassiumcarbonate, ammonium carbonate, sodium hydrogencarbonate, potassiumhydrogencarbonate, ammonium hydrogencarbonate, sodium hydroxide,potassium hydroxide, ammonium hydroxide, or lithium hydroxide. Besidesthese alkaline solutions, it is possible to use an organic amine such asmonoethanol amine, diethanol amine, triethanol amine, monoisopropanolamine, diisopropanol amine, or triisopropanol amine. One of thesecompounds or a combination thereof can be used. As a solvent for thealkaline solution, it is possible to use water, or a mixture of waterand an organic solvent having hydrophilicity, e.g., a lower alcohol.

[0075] The ultraviolet curable resin composition of the presentinvention is particularly suitable to use for the photo solder resistink. However, the application field is not limited to the photo solderresist ink. For example, the resin composition can be used to form aprotective film for color filter. In addition, the resin composition maybe used as a composition for preparing color filter pixels by selectinga suitable coloring agent, for example, an organic pigment such as azolake pigment, insoluble azo pigment and phthalocyanine pigment,inorganic pigment such as iron blue, iron oxide and cobalt, solvent dye,basic dye, disperse dye, or the like.

EXAMPLES Example 1

[0076] The present invention is explained below according to Examples.However, the present invention is not limited to them. Unless otherwisespecified, “parts” and “%” used below is based on weight.

Synthesis Example 1

[0077] A mixture of 70 parts of glycidyl methacrylate, 10 parts of “NKEster 9G” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polypropylene glycol #400 dimethacrylate (n=9), molecular weight=536],20 parts of methyl methacrylate, 100 parts of carbitol acetate, 0.2parts of laurylmercaptan, and 3 parts of azobisisobutyronitrile waspolymerized at a temperature of 80° C. for 5 hours under a nitrogen gasflow in a four-mouth flask, which is provided with a reflux condenser,thermometer, glass tube for nitrogen substitution and an agitator, whilebeing agitated. As a result of this polymerization, a 50% copolymersolution was obtained.

[0078] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 45parts of tetrahydrophthalic anhydride and 79 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-1). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-1) contains 2.9 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 2

[0079] A mixture of 70 parts of glycidyl methacrylate, 10 parts of “NKEster 9PG” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polypropylene glycol #400 dimethacrylate (n=7), molecular weight=536],15 parts of methyl methacrylate, 5 parts of t-butyl methacrylate, 100parts of carbitol acetate and 3 parts of azobisisobutyronitrile waspolymerized at a temperature of 80° C. for 5 hours under a nitrogen gasflow in a four-mouth flask, which is provided with a reflux condenser,thermometer, glass tube for nitrogen substitution and an agitator, whilebeing agitated. As a result of this polymerization, a 50% copolymersolution was obtained.

[0080] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-2). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-2) contains 3.0 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 3

[0081] A mixture of 70 parts of glycidyl methacrylate, 5 parts of “NKEster A-BPE-4” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO.,LTD., 2,2-bis[4-(acryloxy-diethoxy)phenyl] propane, molecularweight=512], 15 parts of methyl methacrylate, 10 parts of cyclohexylmaleimide, 100 parts of carbitol acetate, 0.1 parts of laurylmercaptanand 3 parts of azobisisobutyronitrile was polymerized at a temperatureof 80° C. for 5 hours under a nitrogen gas flow in a four-mouth flask,which is provided with a reflux condenser, thermometer, glass tube fornitrogen substitution and an agitator, while being agitated. As a resultof this polymerization, a 50% copolymer solution was obtained.

[0082] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-3). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-3) contains 3.0 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 4

[0083] A mixture of 70 parts of glycidyl methacrylate, 14 parts of“Blemmer 43 DB-40B ” [manufactured by NOF Corp., bisphenol-Apolyethylene glycol polypropylene glycol adduct dimethacrylate,molecular weight=approximately 1180], 6 parts of methyl methacrylate, 10parts of t-butyl methacrylate, 100 parts of carbitol acetate, 0.3 partsof laurylmercaptan and 3 parts of azobisisobutyronitrile was polymerizedat a temperature of 80° C. for 5 hours under a nitrogen gas flow in afour-mouth flask, which is provided with a reflux condenser,thermometer, glass tube for nitrogen substitution and an agitator, whilebeing agitated. As a result of this polymerization, a 50% copolymersolution was obtained.

[0084] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 105° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-4). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-4) contains 3.0 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 5

[0085] A mixture of 70 parts of glycidyl methacrylate, 10 parts of “NKEster TMPT” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,trimethylolpropane trimethacrylate, molecular weight=338], 15 parts ofmethyl methacrylate, 5 parts of t-butyl methacrylate, 100 parts ofcarbitol acetate, 0.2 parts of laurylmercaptan and 3 parts ofazobisisobutyronitrile was polymerized at a temperature of 80° C. for 5hours under a nitrogen gas flow in a four-mouth flask, which is providedwith a reflux condenser, thermometer, glass tube for nitrogensubstitution and an agitator, while being agitated. As a result of thispolymerization, a 50% copolymer solution was obtained.

[0086] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 105° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-5). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-5) contains 3.3 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 6

[0087] A mixture of 80 parts of glycidyl methacrylate, 20 parts of “NKEster 9PG” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polypropylene glycol #400 dimethacrylate (n=7), molecular weight=536],100 parts of carbitol acetate, 0.2 parts of laurylmercaptan and 3 partsof azobisisobutyronitrile was polymerized at a temperature of 80° C. for5 hours under a nitrogen gas flow in a four-mouth flask, which isprovided with a reflux condenser, thermometer, glass tube for nitrogensubstitution and an agitator, while being agitated. As a result of thispolymerization, a 50% copolymer solution was obtained.

[0088] Next, 0.05 parts of hydroquinone, 42.6 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 45parts of tetrahydrophthalic anhydride and 84 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-6). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-6) contains 3.4 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 7

[0089] A mixture of 70 parts of glycidyl methacrylate, 1 parts of “NKEster 9PG” [manufactured by SHINNAKAMURA CHEMICAL INDUSTRIAL CO., LTD.,polypropylene glycol #400 dimethacrylate (n=7), molecular weight=536],15 parts of methyl methacrylate, 14 parts of t-butyl methacrylate, 100parts of carbitol acetate and 3 parts of azobisisobutyronitrile waspolymerized at a temperature of 80° C. for 5 hours under a nitrogen gasflow in a four-mouth flask, which is provided with a reflux condenser,thermometer, glass tube for nitrogen substitution and an agitator, whilebeing agitated. As a result of this polymerization, a 50% copolymersolution was obtained.

[0090] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-7). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-7) contains 2.9 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 8

[0091] A mixture of 70 parts of glycidyl methacrylate, 20 parts ofmethyl methacrylate, 10 parts of t-butyl methacrylate, 100 parts ofcarbitol acetate, 0.2 parts of laurylmercaptan and 3 parts ofazobisisobutyronitrile was polymerized at a temperature of 80° C. for 5hours under a nitrogen gas flow in a four-mouth flask, which is providedwith a reflux condenser, thermometer, glass tube for nitrogensubstitution and an agitator, while being agitated. As a result of thispolymerization, a 50% copolymer solution was obtained.

[0092] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 100° C. for 24 hours, 45parts of tetrahydrophthalic anhydride and 79 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-8). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-8) contains 2.8 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 9

[0093] A mixture of 70 parts of glycidyl methacrylate, 20 parts ofmethyl methacrylate, 10 parts of cyclohexyl maleimide, 100 parts ofcarbitol acetate, 0.2 parts of laurylmercaptan and 3 parts ofazobisisobutyronitrile was polymerized at a temperature of 80° C. for 5hours under a nitrogen gas flow in a four-mouth flask, which is providedwith a reflux condenser, thermometer, glass tube for nitrogensubstitution and an agitator, while being agitated. As a result of thispolymerization, a 50% copolymer solution was obtained.

[0094] Next, 0.05 parts of hydroquinone, 37 parts of acrylic acid and0.2 parts of dimethylbenzylamine were added to the 50% copolymersolution. After a resultant mixture was kept at 105° C. for 24 hours, 38parts of tetrahydrophthalic anhydride and 72 parts of carbitol acetatewere added to the mixture. The obtained mixture was kept at 100° C. for3 hours to obtain a 50% ultraviolet curable resin solution (A-9). Theultraviolet curable resin (A) of this ultraviolet curable resin solution(A-9) contains 2.9 mol of a polymerizable unsaturated group in 1 kgthereof.

Synthesis Example 10

[0095] 214 parts of “EPICLON N-680” (manufactured by DAINIPPON INK ANDCHEMICALS INCORPORATED, cresol-novolac epoxy resin, Epoxy Equivalents:214) was dissolved in 60 parts of carbitol acetate, while being heated.Next, 74 parts of acrylic acid, 0.1 parts of hydroquinone and 0.7 partsof benzyldimethylamine were added to a resultant mixture, while themixture being agitated, and then kept at a temperature of 90 to 100° C.for 24 hours. In addition, 95 parts of carbitol acetate was added to theobtained reaction solution, and agitated and cooled to obtain an epoxyacrylate solution. Next, 76 parts of tetrahydrophthalic anhydride and 87parts of carbitol acetate were added to the epoxy acrylate solution, andkept at 100° C. for 3 hours to obtain a 60% ultraviolet curable resinsolution (E-1).

Examples 1 to 9 and Comparative Example 1

[0096] A mixture of the ultraviolet curable resin solutions (A-1) to(A-9) and (E-1) obtained in the above-described Synthesis Examples, andother components was prepared according to compounding amounts listed inTable 1, and then kneaded by use of three rolls to obtain liquid photosolder resist inks developable with a diluted alkali aqueous solution ofExamples 1 to 9 and Comparative Example 1.

[0097] In Table 1, “NK Ester A-TMPT-3EO” is trimethylolpropaneEO-denatured triacrylate [manufactured by SHINNAKAMURA CHEMICALINDUSTRIAL CO., LTD., molecular weight=428]. “NK Ester 14G” istriethyleneglycol #600 dimethacrylate [manufactured by SHINNAKAMURACHEMICAL INDUSTRIAL CO., LTD., molecular weight=736]. “EPICLON N-695” isa cresol novolac-type epoxy resin (manufactured by DAINIPPON INK ANDCHEMICALS INCORPORATED). “YX 4000” is an epoxy compound (manufactured byYuka Shell Epoxy Kabushiki Kaisha, epoxy equivalent: 195). “TEPIC-S” istriglycidyl isocyanurate (manufactured by NISSAN CHEMICAL INDUSTRIES,epoxy equivalent : 100). “IRGACURE 907” is a photopolymerizationinitiator (manufactured by CIBA-GEIGY CORPORATION, (2-methyl-1-[4-methylthio(phenyl)]-2-morpholinopropane-1-on)). “KAYACURE DETX-S” is aphotopolymerization initiator (manufactured by Nippon Kayaku Co., Ltd.,2,4-diethyl thioxanthone). “MODAFLOW” is a leveling agent (manufacturedby MONSANTO COMPANY). “SWASOL 1500” is an oil aromatic mixture solvent(manufactured by Maruzen Petrochemical Co., Ltd.).

[0098] In addition, dipentaerythritol hexaacrylate, “NK EsterA-TMPT-3EO” and “NK Ester 14G”, which were used as the ethylenicallyunsaturated photopolymerizable monomer (D-1), respectively contain 10.3mol, 7.0 mol and 2.7 mol of the polymerizable unsaturated group in 1 kgthereof.

[0099] Properties of each of the resist inks and a printed circuit boardwith a solder resist formed by use of the resist ink were evaluatedaccording to the following test methods. Results are shown in Table 2.TABLE 1 Comparative Examples Example 1 2 3 4 5 6 7 8 9 1 Ultravioletcurable resin solution (A-1) 50 Ultraviolet curable resin solution (A-2)50 Ultraviolet curable resin solution (A-3) 50 Ultraviolet curable resinsolution (A-4) 50 Ultraviolet curable resin solution (A-5) 50Ultraviolet curable resin solution (A-6) 50 Ultraviolet curable resinsolution (A-7) 50 Ultraviolet curable resin solution (A-8) 50Ultraviolet curable resin solution (A-9) 50 Ultraviolet curable resinsolution (E-1) 50 Dipentaerythritol hexaacrylate 5 2 2 1 1 2 3 NKEsterA-TMPT-3EO 5 3 3 4 4 3 2 NK Ester 14G 5 5 EPICLON N-695 10 10 10 1010 YX4000 10 TEPIC-S 10 10 10 10 IRGACURE 907 4 4 4 4 4 4 4 4 4 4KAYACURE DETX-S 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 MODAFLOW 1 1 1 11 1 1 1 1 1 Silica (average grain size: 1 μm) 10 10 10 10 10 10 10 10 1010 Barium sulfate 17 17 17 17 17 17 17 17 17 17 Melamine 1 1 1 1 1 1 1 11 1 Phthalocyanine green 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 SWASOL1500 1 1 1 1 1 1 1 1 1 1

[0100] TABLE 2 Comparative Examples Example Test item 1 2 3 4 5 6 7 8 91 Predrying Surface drying time: 10 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ property/tackiness drying time: 20 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Drying drying time: 30min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ temperature Predrying drying time: 10 min ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ (80° C.) time drying time: 20 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯acceptable drying time: 30 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ range drying time: 40min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ (Developing drying time: 50 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯◯ ◯ width) drying time: 60 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ drying time: 70 min ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ drying time: 80 min ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ Δ Δ drying time:90 min ◯ ◯ ◯ Δ Δ ◯ ◯ Δ Δ X Remaining Exposure amount: 50 mJ/cm² 5 5 5 55 5 5 5 5 5 step number Exposure amount: 150 mJ/cm² 8 8 8 8 8 8 8 8 8 8Properties of Resolution ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ test piece Adhesion betweensolder resist and ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ under substrate optimum SolderSoldering Discoloration ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ◯ ◯ ◯ exposure heat (once) towhite resistance Adhesion ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ◯ ◯ ◯ Soldering Discoloration ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ Δ (5 times) to white Adhesion ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ X Pencilhardness 6H 6H 7H 6H 6H 6H 6H 6H 6H 5H Resistance to gold plating ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ Δ Electrical corrosion resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ΔFlexibility ◯ ◯ ◯ ◯ ◯ ◯ ◯ Δ Δ X Flexural endurance ◯ ◯ ◯ ◯ ◯ ◯ Δ Δ Δ X

[0101] Surface Tackiness

[0102] The photo solder resist ink was applied on a surface of a copperclad polyimide film substrate (copper thickness/12 μm: polyimide filmthickness/25 μm) by screen printing. Then, predrying was performed at80° C. to volatilize the solvent from the applied resist ink for threedifferent drying times, i.e., 10, 20 and 30 minutes. As a result, threekinds of predried films having the thickness of about 20 μm wereobtained with respect to each of the photo solder resist inks.

[0103] Subsequently, by use of “ORC HMW680GW” (a low-pressure adhesivetype double-sided exposing machine manufactured by ORC ManufacturingCo., Ltd.), a mask with a required pattern was directly put on each ofthe predried film, and adhered thereto under a reduced pressure. After150 mJ/cm² of ultraviolet light was radiated through the mask, the maskwas removed from the predried film, and the surface tackiness of thepredried film was evaluated according to the following criteria.

[0104] X: It was difficult to remove the mask from the predried film.When the mask was forcedly removed from the predried film, aconsiderable damage of the mask occurred, so that the mask could not beused again.

[0105] Δ: After the mask was removed from the predried film, a sign ofthe mask remained on the predried film.

[0106] ◯: The mask was easily removed from the predried film withoutleaving a sign of the mask thereon.

[0107] Developing Width (Predrying Time Acceptable Range)

[0108] The resist ink was applied on a surface of a copper cladlaminate, which is composed of a glass epoxy substrate and a copper foilhaving the thickness of 35 μm, by screen printing. Then, predrying wasperformed at 80° C. to volatilize the solvent from the applied resistink for nine different drying times, i.e., 10, 20, 30, 40, 50, 60, 70,80 and 90 minutes. As a result, nine kinds of predried films having thethickness of about 20 μm were obtained with respect to each of theresist inks.

[0109] Subsequently, a mask having a required pattern was directly puton the predried film, and adhered thereto. After an optimum amount ofultraviolet light was radiated through the mask, developing wasperformed by use of a 1% sodium carbonate aqueous solution as adeveloper. The developing property and the formed pattern were evaluatedaccording to the following criteria.

[0110] X: It was difficult to remove unexposed portions of the predriedfilm by developing. Therefore, it was impossible to form the pattern.

[0111] Δ: It took an extended time period to develop unexposed portionsof the predried film. In addition, it was impossible to form a finepattern.

[0112] ◯: Unexposed portions of the predried film was easily developedto obtain sharp patterns.

[0113] Remaining Step Number

[0114] The photo solder resist ink was applied on a surface of a copperclad polyimide film substrate (copper thickness/ 12 μm: polyimide filmthickness/25 μm) by screen printing. Predrying was performed at 80° C.for 20 minutes to volatilize the solvent from the predried film. As aresult, two test pieces each having the predried film with the thicknessof 20 μm were obtained with respect to each of the resist inks.

[0115] Subsequently, by use of “ORC HMW680GW” (a low-pressure adhesivetype double-sided exposing machine manufactured by ORC ManufacturingCo., Ltd.), “STEP TABLET PHOTEC 21 steps” (a mask for exposure testmanufactured by Hitachi Chemical Co., Ltd.) was directly put on thepredried film, and adhered thereto under a reduced pressure. 50 mJ/cm²of ultraviolet light was radiated to one of the test pieces through themask. 150 mJ/cm² of ultraviolet light was radiated to the other one ofthe test pieces through the mask. Next, developing was performed by useof a 1% sodium carbonate aqueous solution as a developer. After thedeveloping step, the remaining step number was counted to evaluateexposure sensitivity.

[0116] [Performance Evaluation of Printed circuit board]

[0117] To evaluate a printed circuit board manufactured by use of eachof the photo solder resist inks, test pieces were prepared according tothe following steps (1) to (5).

[0118] (1)<Applying Step>

[0119] The photo solder resist ink was applied by screen printing on asurface of a printed circuit board, which was previously manufactured bypreparing a copper clad polyimide film substrate (copper thickness/12μm: polyimide film thickness/25 μm), and forming a required patternthereon by etching, to thereby obtain a resist ink layer thereon.

[0120] (2)<Predrying Step>

[0121] After the applying step, predrying was performed at 80° C. for 20minutes to volatilize the solvent from the applied resist ink layer, tothereby obtain a predried film having the thickness of 20 μm.

[0122] (3)<Exposing Step>

[0123] Subsequently, the predried film was selectively exposed byputting a mask having a required pattern directly on the predried film,and radiating an optimum amount of ultraviolet light through the mask.

[0124] (4)<Developing Step>

[0125] After the exposing step, unexposed portions of the predried filmwere developed and removed by use of a 1% sodium carbonate aqueoussolution as a developer, to thereby obtain a pattern of the predriedfilm cured by the exposure on the printed circuit board.

[0126] (5)<Post-baking Step>

[0127] After the developing step, the printed circuit board having thepredried film was heated at 150° C. for 30 minutes to cure the predriedfilm. As a result, the test piece having a resist of the cured film wasobtained.

[0128] The following evaluations were carried out with respect to theobtained test pieces.

[0129] Resolution

[0130] By use of a mask pattern having a plurality of slits, which areconcentrically formed such that a slit width and a distance betweenadjacent slits are respectively 40 μm, the pattern of the predried filmwas formed. The resolution of the formed pattern was evaluated accordingto the following criteria.

[0131] X: It was impossible to form the pattern.

[0132] Δ: The pattern was obtained by somehow, but some defects wereobserved.

[0133] ◯: The pattern was accurately formed.

[0134] Solder Heat Resistance

[0135] “LONCO 3355-11” (A water-soluble flux manufactured by LondonChemical Co., Ltd.) was applied as a flux on the test pieces. Next, oneof the test pieces was dipped once in a molten solder bath kept at 260°C. for 15 seconds and washed by water. With respect to the other one ofthe test pieces, this procedure was repeated five times. Subsequently, adegree of discoloration to white was checked according to the followingevaluation criteria. In addition, a crosscut test was performedaccording to JIS (Japan Industrial Standard) D 0202 by use of acellophane adhesive tape.

[0136] X: Discoloration to white considerably occurred.

[0137] Δ: Discoloration to white occurred.

[0138] ◯: Extremely slight discoloration to white occurred.

[0139] ⊚: There was no discoloration to white.

[0140] The adhesion was evaluated according to the following criteria.

[0141] X: Peeling or swelling of the resist occurred before the crosscuttest.

[0142] Δ: Peeling of the resist was partially caused at cross-cutportions by the crosscut test.

[0143] ◯: There was no peeling of the resist.

[0144] Pencil Hardness

[0145] A pencil hardness of the resist was measured according to JIS K5400.

[0146] Resistance to Gold Plating

[0147] Plating was performed on the test piece by use of an electrolessnickel plating bath and an electroless gold plating bath. Then, adhesionof the plated film was checked according to the following criteria toevaluate the resistance to gold plating.

[0148] X: Peeling of the plated film occurred before an adhesive tapewas removed from the plated film.

[0149] Δ: There was no change of appearance of the plated film. However,peeling was partially caused when the adhesive tape was removed from theplated film.

[0150] ◯: There was no change.

[0151] Electrical Corrosion Resistance

[0152] In place of the test piece, a printed circuit board forevaluation was prepared by use of a spit-type electrode B of IPC B-25under the above-explained conditions. After a bias voltage of DC 100 Vwas loaded to the spit-type electrode for 500 hours at the temperatureof 40° C. and the humidity of 90% R.H., the occurrence of migration waschecked. The electrical corrosion resistance was evaluated according tothe following criteria.

[0153] X: The occurrence of migration was confirmed.

[0154] Δ: A slight migration was confirmed.

[0155] ◯: There was no migration.

[0156] Flexibility

[0157] An evaluation test for flexibility was carried out according toJIS K5400. A diameter of a rod that is the test piece is 2 mm. Theoccurrence of cracks was checked.

[0158] Flexural Endurance

[0159] Flexural endurance was evaluated by bending a test substrate intoa 180° angle, and observing the bent portion.

[0160] ◯: No problem

[0161] Δ: Peeling did not occur at the bent portion. However, adiscoloration to white occurred.

[0162] X: Some cracks appeared at the bent portion. Peeling of the curedfilm occurred.

[0163] As clearly understood from Tables 1 and 2, Examples 1 to 9provides improved developing width, solder heat resistance, excellentflexibility and flexural endurance, as compared with ComparativeExample 1. In addition, Examples 1 to 7 each using the ethylenicallyunsaturated monomer component including the compound (ii) at the time ofpreparing the ultraviolet curable resin exhibit particularly improvedsolder heat resistance and flexibility.

INDUSTRIAL APPLICABILITY

[0164] As described above, according to the present invention, it ispossible to provide the ultraviolet curable resin composition having thecapability of forming a cured film with excellent flexibility and solderheat resistance. The photo solder resist ink including this resincomposition is particularly suitable to form a permanent film havinggood flexibility and solder heat resistance on a flexible printedcircuit board, of which demand is growing in recent years.

1. An ultraviolet curable resin composition comprising: (A) anultraviolet curable resin obtained by reacting an epoxy group containingpolymer (a), which is prepared by polymerizing an ethylenicallyunsaturated monomer component including an ethylenically unsaturatedmonomer (i) having an epoxy group and a compound (ii) having at leasttwo ethylenically unsaturated groups in one molecule, with anethylenically unsaturated monomer (b) having a carboxyl group, and thenreacting a resultant intermediate product with a saturated orunsaturated polybasic acid anhydride (c), said ultraviolet curable resinincluding 0.3 to 10 mol of a polymerizable unsaturated group in 1 kgthereof; (B) an epoxy compound having at least two epoxy groups inmolecule; (C) a photopolymerization initiator; and (D) a diluent.
 2. Theultraviolet curable resin composition as set forth in claim 1, whereinthe ethylenically unsaturated monomer component includes anethylenically unsaturated monomer (iii) copolymerizable with theethylenically unsaturated monomer (i).
 3. The ultraviolet curable resincomposition as set forth in claim 1, wherein a content of the compound(ii) having at least two ethylenically unsaturated groups in onemolecule is within a range of 0.1 to 10 mol % with respect to a totalamount of the ethylenically unsaturated monomer component used toprepare the epoxy group containing polymer (a).
 4. The ultravioletcurable resin composition as set forth in claim 3, wherein theethylenically unsaturated monomer component includes an ethylenicallyunsaturated monomer (iii) copolymerizable with the ethylenicallyunsaturated monomer (i) and the compound (ii).
 5. The ultravioletcurable resin composition as set froth in claim 3, wherein the compound(ii) includes di(meth)acrylate.
 6. The ultraviolet curable resincomposition as set forth in claim 3, wherein the compound (ii) isdi(meth)acrylate having at least one oxyalkylene unit.
 7. Theultraviolet curable resin composition as set forth in claim 3, wherein acontent of the compound (ii) is within a range of 0.1 to 10 mol % withrespect to a total amount of the ethylenically unsaturated monomercomponent used to prepare the epoxy group containing polymer (a).
 8. Theultraviolet curable resin composition as set froth in claim 1, whereinthe ethylenically unsaturated monomer (i) includes glycidyl(meth)acrylate.
 9. The ultraviolet curable resin composition as setforth in claim 1, wherein the diluent (D) includes an ethylenicallyunsaturated photopolymerizable monomer having, which contains 3 to 12mol of a polymerizable unsaturated group in 1 kg thereof.
 10. A photosolder resist ink including the ultraviolet curable resin composition asset forth in claim
 1. 11. A photo solder resist ink for manufacturing aflexible printed circuit board, which includes the ultraviolet curableresin composition as set forth in claim
 1. 12. A printed circuit boardwith a permanent film formed by use of the photo solder resist ink asset froth in claim
 10. 13. A flexible printed circuit board with apermanent film formed by use of the photo solder resist ink as set frothin claim
 11. 14. A dry film obtained by forming a film of theultraviolet curable resin composition as set forth in claim 1 on asupport.
 15. A dry film obtained by forming a film of the photo solderresist ink as set forth in claim 10 on a support.